Long Term Evolution-Advanced (Long Term Evolution-Advanced, LTE-A) is a further evolved and enhanced system of a 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP) LTE system. In the LTE-A system, to satisfy a requirement of the International Telecommunication Union for a peak data rate of the fourth generation communications technology, a carrier aggregation (CA) technology is introduced, and is also referred to as a spectrum aggregation (Spectrum Aggregation) technology or a bandwidth extension (Bandwidth Extension) technology. In carrier aggregation, spectrums of two or more component carriers (Component Carrier) are aggregated to obtain a wider transmission bandwidth, and the spectrums of the component carriers may be adjacent and continuous spectrums, or may be nonadjacent spectrums within a same frequency band or even discontinuous spectrums within different frequency bands. It is specified in the LTE Rel-8/9 protocol release that user equipment (UE) can access only one of the component carriers to receive and send data. However, LTE-A user equipment may simultaneously access, according to capability and service requirements of the user equipment, multiple component carriers to receive and send data.
To support technologies such as dynamic scheduling, downlink multiple-input multiple-output (MIMO) transmission, and hybrid automatic repeat, UE needs to feed back multiple pieces of uplink control information (Uplink Control Information, UCI), including channel state information (CSI), hybrid automatic repeat acknowledgement information (HARQ-ACK), a scheduling request (SR), and the like, to abase station eNB by using a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH), where the hybrid automatic repeat acknowledgement information may also be referred to as an ACK (Acknowledgment, acknowledgement information)/NACK (Negative Acknowledgement, negative acknowledgement information) for short.
An existing carrier aggregation system aggregates carriers of a same base station or aggregates carriers of a macro cell and a micro cell that have ideal backhaul (Backhaul). For example, the macro cell and the micro cell are connected by using an optical fiber (where in this case, the micro cell may also be a radio frequency head). In this way, joint scheduling may be performed on multiple carriers, that is, when scheduling one carrier of the aggregation carriers, the base station also knows a status of scheduling on another carrier. In this case, when feeding back an HARQ-ACK to a micro base station, UE generally sends the HARQ-ACK to a macro base station by using a PUCCH on an uplink primary component carrier corresponding to the macro base station, and then the macro base station forwards the HARQ-ACK to the micro base station. Because there is ideal backhaul between the macro base station and the micro base station, both the macro base station and the micro base station may obtain, in real time, the HARQ-ACK fed back by the UE.
In a subsequent evolved LTE system, aggregation of carriers between base stations is introduced. In this case, there is non-ideal backhaul between the base stations, that is, data cannot be switched between the base stations in real time, which causes a result that scheduling of multiple carriers belonging to different base stations is independently performed. That is, when scheduling a carrier of the aggregation carriers, a base station does not know a status of scheduling by another base station on another carrier. In a scenario in which macro and micro cells are coupled that is shown in FIG. 1, a macro cell deployed at frequency f1 mainly provides system information, and performs radio link monitoring and mobility management, to ensure service continuity; and multiple micro cells that are deployed at frequency f2 and that are within a coverage area of the macro cell mainly performs transmission of high data-rate services. There is non-ideal backhaul both between the macro cell and the micro cell, and between the micro cells.
In a CA system between the foregoing base stations, because data scheduling of multiple downlink carriers are independently performed by each base station. For example, the macro base station at the frequency f1 and the micro base station at the frequency f2 perform scheduling independently, and for example, UCI of the carriers is separately fed back to the corresponding base stations. That is, multiple carriers of a UE end transmit the UCI, for example, multiple PUCCHs are transmitted simultaneously, or multiple PUSCHs carrying the UCI are transmitted. Moreover, each base station also independently schedules uplink transmit power of UE, and cannot consider a status of scheduling of the UE by the base station. For the UE end, when a sum of transmit powers of all uplink channels and/or signals that are to be transmitted exceeds a maximum transmit power of the UE, power reduction may be executed in some cases. That is, a power of a signal sent to one or more base stations is reduced, so that a total transmit power of the UE satisfies a requirement of not exceeding the maximum transmit power of the UE.
However, reduction of a power of a signal sent to one or more base stations may cause that the corresponding signal occupies a transmission resource but cannot be correctly demodulated by the base station, thereby reducing overall performance of the system. Moreover, when uplink signals that are sent by the UE end to multiple base stations corresponding to multiple carriers have relatively high timeliness requirements in sending, for example, if the UE needs to simultaneously feed back HARQ-ACK signals to two base stations, reduction of a power of a signal sent by one or more base stations may cause that a HARQ-ACK of downlink data sent by the one or more base stations to the UE cannot be correctly received for a long time, thereby causing ineffectiveness of data transmission, and affecting the overall performance of the system.
To resolve the foregoing technical problem, in the CA system between the foregoing base stations, there may be a type of UE with a relatively low capability, and this type of UE cannot perform uplink sending simultaneously on a carrier corresponding to multiple base stations, and can work, at each moment, on only an uplink carrier corresponding to one base station. When this type of UE works in the CA system between the foregoing base stations, the user equipment with such a capability can also work in the CA system between the base stations by limiting scheduling of the UE by the two base stations or by modifying a time sequence in which the UE feeds back HARQ-ARQs of the downlink data to the base stations or by using another method. Moreover, for this type of UE, a phenomenon that a total power of uplink signals that are sent by a UE end to multiple base stations corresponding to multiple carriers exceeds a maximum transmit power of the UE does not occur.
However, during a process of implementing the technical solutions in the embodiments of this application, the applicant finds that during uplink sending, UE that cannot simultaneously work on an uplink carrier corresponding to multiple base stations can work in a CA system between base stations by using the method in the prior art, and a phenomenon that a total power of uplink signals that are sent by a UE end to multiple base stations corresponding to multiple carriers exceeds a maximum transmit power of the UE does not occur. However, if the UE has a capability of simultaneously working on the uplink carrier corresponding to the multiple base stations, use of the same method causes problems that the capability of the UE is not fully used and scheduling of downlink data may be limited.